PROJECT SUMMARY/ABSTRACT In order to maintain independence into late adulthood, one must be able to safely and reliably participate in Instrumental Activities of Daily Living (IADLs), including taking medications for treatment of chronic conditions. The potential to do this safely without making a medication error depends on a multitude of pre-conditions, including: the number of distinct medications consumed, cognitive status (e.g., dementia), the presence of a caregiver or other mental scaffolds (i.e., medication diary), and cognitive vulnerability (e.g., susceptibility to distraction). Medication errors are numerous ? over a million yearly injuries and 98,000 deaths ? and occur across the spectrum of healthcare (i.e., nurses, physicians, pharmacists, patients), yet little is known about medication errors in daily life. For this R03, we are specifically interested in understanding the types of medication errors made in daily life, and discovering person-specific and situation-specific risk factors for medication errors in the home. Perceptions of medication administration problems, medication regimen complexity, and the nature of medication errors in the home and their consequences will be assessed in older adults currently recruited into the Einstein Aging Study (EAS), using an innovative three-pronged medication assessment (i.e., daily EMA of medication administration problems, medication error history interview with study neurologist, medication possession ratios from EHRs). Making use of existing clinical data (i.e., ratings of MCI), and cognitive performance data (both in-lab and ambulatory assessments) we will identify person-specific and situation-specific risk factors for various types of medication errors. Completion of this work will highlight actionable targets for future interventions targeting the reduction of medication errors.